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Topic: New Mobile Wood Oven Problems (Read 6588 times)

I have just collected a new mobile wood oven for a new business. I am having problems getting the floor anywhere near the 650 deg F I need for the Neapolitan pizza I want to cook. I am in touch with the builder I need to know if this is a design fault and it will never be fit for purpose in which case I need to return or if it`s something that can be fixed.

I am burning kiln dried oak [less than 20% moisture) and lots of it but cannot get an infrared reading above 500 deg F anywhere on the floor. Fires are to one side, sometimes for 4 hrs plus. Flame lapping dome, dome white in places. 1m x 1m internal cooking floor. Fire brick floor,not set (ie removable)1 inch deep bricks, then 1.5 inch white foam board, then sheet metal base that sits on a mobile trailer. Exterior oven does not get hot, warm maybe on side of fire. Underneath metal base does not get hot either. Sorry, barrel vault design.

I would appreciate any advice. I have start dates in restaurants soon I can`t cook one pizza let alone 50.

Not sure I understand this. Typically, the fire is started in the center of the deck and only pushed to the side just before you start baking. Do have photos/specs of your oven? Also photos of the firing and baking? How much wood are you using to fire it up? Is this wood oven designed for pizzas? Have you tried firing it with as much wood as will fit just to see it that helps?

Barrel shape may not be optimum. Opening may be too big allowing heat to escape. Sounds like there is adequate insulation, but you need a high thermal mass so that, once up to temperature, the deck maintains enough heat to bake for the entire session.

I am sorry to hear about your problems getting the floor up to temp. If you have a fire burning for 4 hours and the floor is only 500, then there is either a serious design flaw or you are not firing it properly. What is the temperature of the dome?

And I agree with Bill. 650 is way too low for Neapolitan pizza. Your floor should be 750 or higher for under 2 minute bakes.

Did you try baking a pizza in it, just to see how it goes?Nice instruments, those lasers, but I just throw a pinch of flour on the floor and watch how fast it browns.

Never heard of floor getting not hot enough, usually it gets too hot. If those are normal fire bricks, and the dimensions of the oven are just and the opening isn't too big, everything should be working out. You start stoking the oven with thin wood, sticks and branches, so there's lot of air-space and it burns fast and hot. When most of the dome is becoming clean then you switch to bigger wood and move the fire to the side.

whoops I missed that. I was reading from my mobile phone in bed! Well it sounds like heat is exiting the front entrance then. Do you guys think the type of firebrick matters? Even if he is losing heat from the front, a 4 hour fire (anyway you fire it) should get a floor temp of above 500 easy. Something really strange is going on here. Instead of trying to figure it out, if the OP is press for time, he might consider returning it and getting a different oven. It could be an easy fix or it could not.

How long have you had the oven? Did you cure it or was it already cured when you bought it? If you cured it how was it cured? Is it exposed to the elements? How is the enclosure built?

I ask all these things because it sounds like the oven is wet. It could be wet because it is not yet fully cured, or it could be wet because the enclosure is not water tights and it is exposed to the elements.

Let me give you what I can now, I will post pics as soon as possible. Cooking for family tomorrow so I will document thoroughly.

Hi Bill,

Thankyou,

1. This for a commercial project - the initial fire is started in the front middle for air draw and moved to the side once established. Obviously I can do this only once at the start of a 3 -4 hr service.2. I will post pics soonest. I know it makes assessment much easier.3. Starting fire with firelighter and dry softwood kindling, moving to small hardwood and then to kiln dried oak hardwood logs (2 -3 inch dia, 10 -12 inch long, tested under 20% moisture). Using too much to be commercially viable!4. Yes the oven is designed specifically for pizza. Italiano Forno oven.5. I will saturate the oven tomorrow.6. The oven opening is 18 inch wide and 11 inch at the apex of arch.7. Right now 650 F would be a blessing!. I can make allowances with my dough at this level but can`t work with 500 F.

Hi Dellavecchia,

Thankyou, I hope it`s me. It will be the easiest solution. The max temp for centre of the dome with flame lapping over was approx 800 F. I will record again tomorrow.

Hi Dirk3000,

Thankyou, Yes I have baked pizza. 64% hydration and couldn`t get it off the floor. My fault for putting it in when I knew the temp wasn`t there. Like waiting for a late bus. Hope pics will explain the materials better. I`m no oven builder.

Chau,

Thankyou, bottom insulation is my big worry due to remedy difficulty but as Bill says the underside metal is on barely warm. The oven builder is being arsey (uk for difficult). He says the oven has the capacity. Says I should be using just seasoned logs (20 -30% moisture) not kiln dried against all suppliers/operators I have researched, blames my fire building. Chau, I hope for an easy fix so I get on with making pizza.

Hi Shuboyje,

Thankyou, I collected the oven on Sunday. The builder said he had cured but the first fire I made at the end there were visible rust colour runs down the trailer side. I assumed moisture but after 3 more fires they have stopped. I assume the oven will continue to improve with use but unsure if this explains the temp issue. The oven is encased in metal. I cannot see how rain would penetrate. When cooled the oven door is closed and I put a cover over the chimney. Had no rain here this week anyway - surprise you?. I know we are famous for it.

1. This for a commercial project - the initial fire is started in the front middle for air draw and moved to the side once established. Obviously I can do this only once at the start of a 3 -4 hr service.

Barnstable: Thanks for the information. I would say this might be part of the problem. Try building the fire in the exact middle of the oven and keep it there until shortly before baking. The spot where the fire was should be hot enough for baking. This is only done once at the start of the day. If the oven is designed correctly, the coals and fire off to the side should keep the oven hot throughout the service. If for some reason, you need to have the fire close to the front, then there is either a design flaw in the oven or you need to work on your fire management.

Is there any sort of vent in the metal enclosure? If there is still moisture inside it will need someplace to escape. Your ovens performance sounds like a dead ringer for moisture problems to me. An oven would have to be very poorly designed and built to perform like that dry. Dry stacked piles of brick built in a few hours with no insulation will out perform what you are describing. I do question the builder a bit as your description does not sound anything like an italian oven which is what it sounds like you were told it was, but I still stand by the fact that it cannot possibly be so poorly built that this is as good as it can perform.

Here is another question I don't think has been asked yet. Where is the flue entrance located in your oven?

Thank you I will try this tomorrow although to be honest I have had fires all over the oven. There is no requirement to have the fire centre most front I just understood it to be best practice initially to encourage good air draw from flue. I will start the fire in the direct centre of the cooking floor. I will continue to develop the fire in the same postion regardless of size. Just prior to cooking I will move to the side. Sweep oven and take a reading prior to every pizza loaded. The reason I chose a larger cooking floor was because I anticipated cooking 2/3 pizza at one time to accommodate a `restaurant` demand. This is supposedly well within the capability of the oven. Also, it is what I will need.

Hi Shuboyje,

Thank you, the flue/chimney is situated 3/4 inches inside the oven, ie from oven entrance. From the internal oven roof to the external top 26 inches. Chimney external dia approx 7 inches. Internal looks more like 3 inches. Difficult to see but can confirm if important.

I would like to thank you for your advice, tips and for being interested in helping in the first place. It seems I was certainly a big part of the problem. Thank you especially Bill. My bake on Sunday was much more encouraging.

I positioned the fire in exact centre as Bill suggested and kept it there until cooking time. I also built the biggest fire by far I have tried. I think my problem was in thinking I had a good fire already and by applying logs regularly through a 3/4 hr period the oven would get hotter with time. I clearly didn`t. And it didn`t. I understand now that I must first saturate the oven with temperature (almost overkill) at the outset and then not only will I be able to reach a good cooking temp initially but have a better chance of maintaining it over a service period.

The oven is the italiano forni that parrelei found, just bigger. I let the fire burn for 45 minutes with the door closed ( designed with half in gap underneath when `closed`), moved to the side and swept. The first floor reading must have been over 1000 F as the gun went negative. Huge relief. Never so happy to see a burnt bottom on garlic bread.

Floor was 850 F when the first pizza went in and had to keep in the air for most of bake to balance the top. I tried to keep the door closed as much as possible. I kept the fire going after the bake to test heat maintenance and after 2 hrs 15 mins the floor was 630 F and the dome 710 F. At this point the underside of the oven ( which I last stated as only being warm because my fire was not big enough presumably) was 223 F. Before I choke on a big peice of humble pie with the builder is this about right?

I`d appreciate any other advice on heat maintenance for a neapolitan bake over a 3/4 hr service.

My father took pics but hasn`t sent them through yet (old folk) but you may not be interested now I`ve stopped panicing - a bit.

Kind regards,

Barnstable

ps When your US spell check prompts my spelling of centre I ignore it. Is that naughty

Happy to hear you are having better luck with the oven. As for the builder, I certainly wouldn't give them to much credit. Over 200F outside the insulation is way to hot, and having a chimney inside the oven chamber at the top is another major design flaw. If I am understanding you correctly I don't think the oven is currently performing to the level you will need to cook neapolitan pizzas for a few hours, but possibly as you get to know the oven better and learn to manage the fire more it could. Leaking heat out the top due to the improper vent and the bottom due to lack of insulation is gonna make it a bit of a challenge though.

For neapolitan Pizza you are going to want a minimum floor temperature of 800F. Normally once you get the oven up to temperature you would fire it in the center slightly longer to saturate the thermal mass. You would then move the fire to one side and from that point on a small amount of wood added to the fire as it burns down should maintain the temperature for as long as you need it. My understanding is under this situation your oven dropped to 630F on the floor in only a couple hours?

I'm so glad you are seeing progress! There is probably no more challenging kind of cooking than with a WFO. I've been doing it now for 12 years and am still improving my skills! I agree with shuboyje. The temps you are measuring on the outside surfaces indicate inadequate insulation. And the temp drops indicate insufficient thermal mass (or under-firing).

One thing you could do, which may be a PITA would be to alternate the coal bed from one side of the deck to the other in the hopes of baking each pizza on the hottest area of the deck. I've used this method when I have miscalculated and under-fired the oven. Also, In order to keep the fire as hot as possible, I throw several smaller chunks of wood on the fire rather than a larger log. These pieces will ignite and release heat faster.

Sorry they are late but here are some pics of last Sundays bake. I hope you can get a better idea of the oven. I`d be grateful if you could look at it and give me an opinion. I`m trying to understand if I will be banging my head against a brick wall and it`s better to back it to the builder no matter what the problems ie, legal action, time, no oven or if it`s my inexperience with fires or if I can make some remedies myself.

Bill, 12 years...mmm...only 11 yrs and 51 weeks to reach you. Seriously, I am always happy if it`s my shortcomings/inexperience that needs attention. Within my control. Thanks for the tip re switching coals. nice to have an emergency strategy but obviously I don`t want this to be standard. I also think I might use too big logs later in the bake, thanks.

Bill/Shuboyje,

This is the crux. Chimney and insulation. Now you can see the oven is the chimney unworkable. Also, is there a DIY solution. Can I reduce the chimney girth? Would it help? The oven floor fire bricks are not set and also a touch uneven which is snagging my peel (i know they are bad but wanted to get the feel/size of oven before commiting). Is there a form of self levelling insulation that I could reset the bricks on of minimal depth that could kill two birds with one stone?

I have 0 experience with mobile WFO's. Your photos are pretty small, but if the chimney is within the cooking chamber, which it looks like it might be, then I see that as a serious, possible fatal, problem. The whole issue of air flow needs to be just right so that you can support a nice,hot, non-smoldering fire, but that as much of the energy is trapped within the cooking chamber heating the decks, wall, and dome. Heat escaping through the flue or opening needs to be minimized. This balance is one of the most important aspects of a good oven design. If you try to decrease draw out the chimney, you could choke off the fire. Give it a try.

If you are looking to experiment with the flue I would not restrict it, I would instead put an extension on into the oven chamber that terminates at 63% of the dome height. Not ideal but should keep the heat in the oven rather then up the flue

Thanks for the flue suggestion. I think I could muster up just such an extension even if only temperary so that I can then test the heat performance again. Would you suggest it comes down to 63% of the dome height in a vertical line of angled towards the oven entrance if possible. The other issue is the temperature of the oven underside when baking. Mine was 220 F, if this is too high can I ask in your opinion what a normal/acceptable temperature would be?. Any thoughts on the suggestion of lifting the bricks and adding a thin but effective additional layer of insulation and if there is a material that would be suitable?.